| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1982300 | Insect Biochemistry and Molecular Biology | 2011 | 11 Pages |
Insect host/parasitoid interactions are co-evolved systems in which host defenses are balanced by parasitoid mechanisms to disable or hide from host immune effectors. Although there is a rich literature on these systems, parasitoid immune-disabling mechanisms have not been fully elucidated. Here we report on a newly discovered immune-disabling mechanism in the Pieris rapae/Pteromalus puparum host/parasitoid system. Because venom injections and parasitization suppresses host phagocytosis, we turned attention to the P. rapae scavenger receptor (Pr-SR), posing the hypothesis that P. puparum venom suppresses expression of the host Pr-SR gene. To test our hypothesis, we cloned a full-length cDNA of the Pr-SR. Multiple sequences alignment showed the deduced amino acid sequence of Pr-SR is similar to scavenger receptors of other lepidopterans. Bacterial and bead injections induced Pr-SR mRNA and protein expression, which peaked at 4 h post-bead injection. Venom injection inhibited Pr-SR expression. Pr-SR was specifically expressed in granulocytes compared to plasmatocytes. We localized the Pr-SR protein in cytoplasm and cellular membrane, with no evidence of secretion into host plasma. Double-strand RNA designed to Pr-SR mRNA silenced expression of Pr-SR and significantly impaired host phagocytosis and encapsulation reactions. Venom injections similarly silenced Pr-SR expression during the first 8 h post-treatment, after which the silencing effects gradually abated. We infer from these findings that one mechanism of impairing P. rapae hemocytic immune reactions is by silencing expression of Pr-SR.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (123 K)Download as PowerPoint slideHighlights► We report a new venom-linked immune-disabling mechanism in an insect parasitoid. ► Pteromalus puparum venom treatments inhibit Pr-SR expression induced by infection. ► Silencing Pr-SR expression cripples host phagocytosis and encapsulation reactions. ► The influence of P. puparum venom was expressed in a time- and dose-dependent manner. ► P. puparum venom blocks expression of specific genes required for cellular immunity.
